Simple analysis of diphenylmethane antihistaminics and their analogues in bodily fluids by headspace solid-phase...

Thirteen antihistaminic drugs and their analogues are tested for their extraction by headspace solid-phase microextraction from human whole blood and urine. Their determination is made by using capillary gas chromatography with flame ionization detection. Relatively high recoveries are obtained for terodiline, diphenhydramine, diphenylpyraline, and orphenadrine in urine; but the recoveries in blood extracts are 4-51 times lower than those in urine extracts for all drugs. Benactyzine and piperilate are not suited for the extraction method. The calibration curves are drawn for four drugs spiked to whole blood and for eleven drugs spiked to urine; excellent linearity is confirmed for the drugs. The detection limits for the drugs are 76-473 ng/mL in blood and 13-186 ng/mL in urine. Diphenhydramine is determined for whole blood obtained from a male subject who had received oral administration of 30 mg diphenhydramine-HCl 150 min before the sampling; the concentrations of the drug are 0.12 and 1.22 micrograms/mL for blood and urine, respectively.